(1) Field of the Invention
The present invention relates generally to sandwich belt endless conveyor systems, and more particularly to an improved sandwich belt conveyor system which will carry large volume of product up very steep slopes without loss of product or damage to the product.
(2) Background Information
Belt conveyors have been utilized for many years to transport bulk materials, including granular materials, between various levels. However, single belt conveyors are restricted to a very shallow angle, because of the back flow of material being conveyed.
To overcome this problem, a pair of dual endless flexible conveyor belts are engaged in face to face relationship to trap the bulk material therebetween and convey the bulk material at very steep vertical angles. These dual belt systems, commonly referred to as sandwich belt systems, have taken on various forms to convey bulk materials. For example, U.S. Pat. No. 3,910,405 to Couperus et al., discloses a first belt with raised edges which engage and seal with the edges of a second belt. A plurality of protruding cleats on the belt assist in carrying bulk granular material along a steep slope.
U.S. Pat. No. 4,195,724 to Janitsch discloses a sandwich belt conveyor utilizing staggered rollers to urge the edges of the belts into engagement with one another to reduce leakage or spillage of material. The edges of the belts are stretched in following a sinuous path between the edge rollers, causing the confronting belt edges to firmly engage one another.
U.S. Pat. No. 4,585,118 to Plaut discloses a sandwich belt system with special rollers designed to provide automatic tracking and centering of the belts of a dual belt conveyor system.
While such sandwich belt systems have been effectively utilized to transport sludge, sewage, slurry-type materials and solid or semi-solid bulk material, they still have a number of problems when used for transporting granular materials such as seed and the like. The main problem of prior art sandwich belt systems is in the squeezing pressure between the belts in order to carry the granular material up steep inclines. If the belts are squeezed together too tightly, the seed can be damaged. On the other hand, if the belts are not squeezed tightly enough together, the seed can escape from between the belts.
It is therefore a general object of the present invention to provide an improved sandwich belt conveyor system.
Another object of the present invention is to provide a sandwich belt conveyor system which will carry large volumes of granular product up very steep inclines, without damage to the granular product.
A further object is to provide a sandwich belt conveyor system which will carry large volumes of granular product up steep inclines without loss of product.
These and other objects of the present invention will be apparent to those skilled in the art.
The dual belt conveyor of the present invention includes a pair of flexible endless loop conveyor belts arranged at an incline with a lower flight of the upper belt in face-to-face conveying relationship with an upper flight of the lower belt to retain and convey granular material between the belts. Drive pulleys are connected to both belts to move the belts at the same speed, and the conveying flights of the belts are journaled through a trough which forces the belts into a curved concave orientation between the side edges with the upper belt biased downwardly into engagement with product on the lower belt to retain product therebetween.